Acid synthesis process



Patented Mar. 10, 1936 ET STATES Aorn SYNTHESIS rnooass NoDrawing, Application March 25, 1933, Serial No. 662,853

6- Claims.

This invention relates to an improved process for the preparation of organic acids by the interaction of olefinic hydrocarbons with carbon monoxide and more particularly to the materials of construction in which such organic acid syntheses are conducted.

Mixtures of unsaturated hydrocarbons have been exposed repeatedly with carbon monoxide in the presence or absence of water vapor, to the action of catalysts under conditions varying as to the nature of the catalyst and as to the temperature and pressure prevailing in the reaction, with the result that methane, liquid hydrocarbons, carbonyls, and/or products of the water-gas re- 5 action have been obtained in greater or lesser amounts and in inverse proportion to the acid desired.

More recently, due, no doubt, to the development of more selective catalysts high yields of 20 the desired products have been realized with a corresponding decrease in the production of the undesirable by-products. When employing these more selective catalysts, however, it has been found that their life is relatively short-while 25 methane, polymerization products, and carbonyls are still present in annoying amounts.

An object of the present invention is to provide an improved process for the preparation of organic compounds of an acidic nature from olefinic 30 hydrocarbons and carbon monoxide and steam by conducting the reaction involving these compounds in an environment which overcomes many of the above disadvantages. Another object of the present invention is to provide an improved 35 acid synthesis process wherein the reactants or the products formed therefrom contact with metal surfaces which inhibit by-product formation. A still further object of the invention is to provide improved acid synthesis from olefines,

40 carbon monoxide, and steam in equipment fabricated from metals which do not cause the olefin-e to polymerize, or form products with, the reactants, such as carbonyls with carbon monoxide, or catalyze reactions such as the water-gas re- 45 action, or deteriorate the catalytic mass employed. Other objects and advantages will hereinafter appear.

I have found that in order to avoid polymerization, excessive by-product formation, with its 60 attendant loss of reactants, and at the same time in order to decrease catalyst deterioration, the various parts of the acid synthesis apparatus coming into direct contact with the reactants must be fabricated of, or parts thereof which 55 contact with the reactants plated, innerlined, or

otherwise treated with a metal which under the high temperatures and pressures prevailing is effective in resisting such action. For the hot parts of the apparatus, i. e. all those parts with which the highly heated reactants contact with 5 the apparatus, there should be employed, I have found, a pressure-resisting shell the inner surfaces of which, as well as all other surfaces contacting the reactants, are lined with a metal containing at least 90% silver, whereby by-product 10 formation and rap-id catalyst deterioration can be inhibited, and in many instances entirely eliminated. The cooler parts of the apparatus may be fabricated of a low carbon steel containing a silver inner lining or one of copper, glass, or enamel, or of an unlined alloy containing, for example, approximately 95% copper, 4% silicon, and 1% manganese, or one containing approximately 58% nickel, iron, 28% molybdenum, and 2% manganese. It is, of course, understood 20 that it is unnecessary to line the complete conversion apparatus with a single material, for it is generally preferable to line the portions- 0f equipment which contact with the hot reactants with one metal and those which contact with the cooler reactants and/or products formed with a different metal. For example, an excellent pressure-resisting metal for the construction of the catalytic reaction chamber and preheater through which the reacting gases pass prior to 30 entering the reaction chamber, may, with very good results, be constructed of an alloy steel having approximately the following composition: 61% nickel, 11% chromium, 2.25% tungsten, 1.4% manganese, 0.3% carbon and 25% iron, the remainder other metals in smaller amounts, the inner surfaces being lined with silver; while the apparatus which feeds the gaseous materials to the reaction chamber as well as that utilized for condensing and recirculating the cooler products may be constructed of a low carbon steel with an inner lining of copper or silver.

Although the metals above referred to are capable of withstanding for no inconsiderable periods the rigorous conditions of very high temperatures and pressures encountered in the operation of such syntheses, I have likewise found that their period of usefulness can be still further extended by a substantially complete elimination of oxygen from the mixture of reactants. It is believed that oxygen present in the system acts somewhat in the capacity of a catalyst which accentuates many of the undesirable conditions and reactions referred to. Moreover, its presence aids corrosion which, of course, is invariably prescut in acid synthesis processes and particularly when catalysts of an acidic nature are used. For most advantageous operation, therefore, of acid synthesis processes, even when conducting it in equipment prepared in accord with my invention, oxygen, in the free state, should be substantially entirely eliminated. A method and process for its elimination from the reactants is described in the copending A. T. Larson application Ser. No. 651,858, filed January 14, 1933.

The following example will serve to illustrate one manner of carrying the invention into eifect without limiting it in any way to the exact details therein designated. An alloy steel catalyst tube, such as that specifically designated above and capable of resisting high pressure, is lined inside with a contiguous fine silver lining. This catalyst chamber is partially filled with activated charcoal and after bringing the chamber and charcoal catalyst to approximately 325 C., a gaseous mixture containing, by volume, 95 parts of carbon monoxide and 5 parts ethylene, is passed into the chamber, at a pressure of approximately 700 atmospheres, together with sufficient steam to give a steam:carbon monoxide and ethylene ratio of 0.25, the steam being provided by injection of the appropriate amount of a 1% aqueous solution of ammonium chloride. A 75% yield of propionic acid is obtained with a surprisingly small amount of by-products, polymerization products, and other undesirable products.

From a consideration of the present invention it will be realized that acid synthesis processes in which olefinic hydrocarbons are reacted with carbon monoxide and steam, conducted in apparatus constructed of metals and operated in the manner as hereinbefore described, will come within the scope of this invention without sacrificing any of its advantages.

I claim:

1. In the manufacture of synthetic aliphatic monocarboxylic acids by the catalytic addition of carbon monoxide and water to olefinic hydrocarbons at elevated temperature and pressure, the

. step which comprises conducting the reaction in an apparatus, the inner surfaces, which contact with the reaction, comprising a metal containing at least 90% silver.

2. In the manufacture of synthetic aliphatic monocarboxylic acids by the catalytic addition of carbon monoxide and water to olefinic hydrocarbons at elevated temperature and pressure, the step which comprises conducting the reaction in an apparatus, the inner surfaces, which contact with the reaction, being fabricated of an alloy containing at least 90% silver.

3. In the manufacture of synthetic aliphatic monocarboxylic acids by catalytic addition of carbon monoxide and water to olefinic hydrocarbons at elevated temperature and pressure, the step which comprises conducting the reaction in an apparatus the inner surfaces of which are lined with silver.

4. In the manufacture of synthetic aliphatic monocarboxylic acids by the catalytic addition of carbon monoxide and water to olefinic hydrocarbons at elevated temperature and pressure, the step which comprises conducting the reaction in the substantial absence of oxygen in an apparatus, the inner surfaces, which contact with the reaction, comprising a metal containing at least 90% silver.

5. In the manufacture of synthetic aliphatic organic monocarboxylic acids by catalytic addition of carbon monoxide and water to olefinic 

